1. Field of the Invention
The present invention relates to fibre channel systems, and more particularly, to improving fibre channel switch efficiency.
2. Background of the Invention
Fibre channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware.
Fibre channel fabric devices include a node port or “N_Port” that manages fabric connections. The N_port establishes a connection to a fabric element (e.g., a switch) having a fabric port or F_port. Fabric elements include the intelligence to handle routing, error detection, recovery, and similar management functions.
A fibre channel switch is a multi-port device where each port manages a simple point-to-point connection between itself and its attached system. Each port can be attached to a server, peripheral, I/O subsystem, bridge, hub, router, or even another switch. A switch receives messages from one port and automatically routes it to another port. Multiple calls or data transfers happen concurrently through the multi-port fibre channel switch.
Fibre channel switches use memory buffers to hold frames received (at receive buffers) and sent across (via transmit buffers) a network. Associated with these buffers are credits, which are the number of frames that a buffer can hold per fabric port.
In conventional switches a link may be reset (for various reasons), and before the link goes up, it must free up receive buffers so that it has full credit. However, frame flow is halted in other links that are not affected by the reset. Hence, during reset of a link, other unaffected links stay idle. This is inefficient and affects overall performance.
Also, often frames wait in transmit buffers (for whatever reason) and cause congestion. Conventional switches do not allow efficient disposal of such frames.
Therefore, what is required is a method and system for fibre channel switches that can flush the buffers without disrupting frame flow in unaffected links, and also divert frames that have been waiting for transmission.